Environmental fate of alkylphenols and alkylphenol ethoxylates—a review

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Abstract

Alkylphenol ethoxylates (APEs) are widely used surfactants in domestic and industrial products, which are commonly found in wastewater discharges and in sewage treatment plant (STP) effluents. Degradation of APEs in wastewater treatment plants or in the environment generates more persistent shorter-chain APEs and alkylphenols (APs) such as nonylphenol (NP), octylphenol (OP) and AP mono- to triethoxylates (NPE1, NPE2 and NPE3). There is concern that APE metabolites (NP, OP, NPE1–3) can mimic natural hormones and that the levels present in the environment may be sufficient to disrupt endocrine function in wildlife and humans. The physicochemical properties of the APE metabolites (NP, NPE1–4, OP, OPE1–4), in particular the high Kow values, indicate that they will partition effectively into sediments following discharge from STPs. The aqueous solubility data for the APE metabolites indicate that the concentration in water combined with the high partition coefficients will provide a significant reservoir (load) in various environmental compartments. Data from studies conducted in many regions across the world have shown significant levels in samples of every environmental compartment examined. In the US, levels of NP in air ranged from 0.01 to 81 ng/m3, with seasonal trends observed. Concentrations of APE metabolites in treated wastewater effluents in the US ranged from <0.1 to 369 μg/l, in Spain they were between 6 and 343 μg/l and concentrations up to 330 μg/l were found in the UK. Levels in sediments reflected the high partition coefficients with concentrations reported ranging from <0.1 to 13,700 μg/kg for sediments in the US. Fish in the UK were found to contain up to 0.8 μg/kg NP in muscle tissue. APEs degraded faster in the water column than in sediment. Aerobic conditions facilitate easier further biotransformation of APE metabolites than anaerobic conditions.

Introduction

Alkylphenol ethoxylates (APEs) are one of the most widely used classes of surfactants. They have been used in domestic detergents, pesticide formulations and industrial products. Octylphenol ethoxylates (OPEs) and nonylphenol ethoxylates (NPEs) are two of the most common surfactants in the marketplace. APEs are discharged to wastewater treatment facilities or directly released into the environment. Primary degradation of APEs in wastewater treatment plants or in the environment generates more persistent shorter-chain APEs and alkylphenols (APs) such as nonylphenol (NP), octylphenol (OP) and AP mono- to triethoxylates (NPE1, NPE2 and NPE3) (Giger et al., 1984). Many studies have reported on the wide occurrence of APE metabolites in the environment (e.g., Ahel and Giger, 1985, Naylor et al., 1992, Bennie et al., 1997, Blackburn et al., 1999, Ferguson et al., 2001, Tabata et al., 2001).

Studies have found that APE metabolites are more toxic than the parent substances and possess the ability to mimic natural hormones by interacting with the estrogen receptor Soto et al., 1991, Jobling and Sumpter, 1993, Jobling et al., 1996, Renner, 1997. The levels of these APE metabolites present in the environment may be well above the threshold necessary to induce endocrine disruption in wildlife. These findings have raised public concern over their environmental and human health effects.

In order to assess the risks associated with these substances, it is necessary to understand the distribution and fate of APEs and their metabolites in the environment. This review will focus on current knowledge on the behaviour and fate of APE metabolites (NP, OP, NPE1–3) and related compounds in the environment.

Section snippets

Uses and exposure

APEs are a class of surfactants which are manufactured by reacting APs with ethylene oxide. An APE molecule consists of two parts: the AP and the ethoxylate (EO) moiety. This structure makes APEs soluble in water and helps disperse dirt and grease from soiled surfaces into water.

APEs can be used as detergents, wetting agents, dispersants, emulsifiers, solubilizers and foaming agents. APEs are important to a number of industrial applications, including pulp and paper, textiles, coatings,

Physicochemical properties

The physicochemical properties determine the behaviour of APE metabolites in the environment. Table 1 lists some physicochemical properties for APE metabolites (NP, NPE1–4, OP and OPE1–4). The solubility of an APE surfactant depends on the number of polar groups forming the hydrophilic part of the molecule. Lower APE oligomers (EO<5) are usually described as “water-insoluble” or lipophilic, whereas the higher oligomers are described as “water-soluble” or hydrophilic (Ahel and Giger, 1993a). The

Levels in the environment

APEs and their degradation products (e.g., NP and OP) are not produced naturally. Their presence in the environment is solely a consequence of anthropogenic activity. APs and APEs enter the environment primarily via industrial and municipal wastewater treatment plant effluents (liquid and sludge), but also due to direct discharge such as through pesticide application. The distribution of APs and their EOs has been documented in many studies in North America and Europe. NP, OP and NPEs were

Fate in the environment

APEs make up the world's third largest group of surfactants in terms of production and have been used widely in the industry for about 50 years. Concern has increased recently about the use of APEs because of the relative stability of their metabolites (NP, OP, NPE1–3) in the environment (Giger et al., 1984) and their estrogenic character to organisms like fish (Jobling and Sumpter, 1993). To assess their environmental risk, it is necessary to understand the behaviour and fate of APEs in the

Summary

(1) APEs are one of the widely used surfactants in the world. Their metabolites (NP, OP, NPE1–3) are ubiquitous in the environment because of their wide use patterns and the widespread lack of adequate wastewater treatment, and these compounds have been detected in air, water, sediment, soil and biota at differing levels in different parts of the world.

(2) Physicochemical properties indicate that APE metabolites are hydrophobic substances. They tend to bioaccumulate in lipids of organisms in

References (70)

  • W.H. Ding et al.

    Occurrence and concentrations of aromatic surfactants and their degradation products in river waters of Taiwan

    Chemosphere

    (1999)
  • R. Ekelund et al.

    Biodegradation of 4-nonylphenol in seawater and sediment

    Environ Pollut

    (1993)
  • M. Hawrelak et al.

    The environmental fate of the primary degradation products of alkylphenol ethoxylate surfactants in recycled paper sludge

    Chemosphere

    (1999)
  • S.J. Jobling et al.

    Detergent components in sewage effluent are weakly oestrogenic to fish: an in vitro study using rainbow trout hepatocytes

    Aquat Toxicol

    (1993)
  • A.C. Johnson et al.

    The sorption of octylphenol, a xenobiotic oestrogen, to suspended and bed-sediments collected from industrial and rural reaches of three English rivers

    Sci Total Environ

    (1998)
  • H.B. Lee et al.

    Determination of nonylphenol polyethoxylates and their carboxylic acid metabolites in sewage treatment plant sludge by supercritical carbon dioxide extraction

    J Chromatogr, A

    (1997)
  • R.M. Mann et al.

    Biodegradation of a nonylphenol ethoxylate by the autochthonous microflora in lake water with observations on the influence of light

    Chemosphere

    (2000)
  • M.A. Manzano et al.

    The effect of temperature on the biodegradation of a nonylphenol polyethoxylate in river water

    Water Res

    (1999)
  • J.P. Salanitro et al.

    Anaerobic biodegradability testing of surfactants

    Chemosphere

    (1995)
  • M.J. Scott et al.

    The biodegradation of surfactants in the environment

    Biochim Biophys Acta

    (2000)
  • M. Sekela et al.

    Occurrence of an environmental estrogen (4-nonylphenol) in sewage treatment plant effluent and the aquatic receiving environment

    Water Sci Technol

    (1999)
  • C.A. Staples et al.

    Measuring the biodegradability of nonylphenol ether carboxylates, octylphenol ether carboxylates and nonylphenol

    Chemosphere

    (1999)
  • T. Tanghe et al.

    Nonylphenol degradation in lab scale activated sludge units is temperature dependent

    Water Research

    (1998)
  • T. Tsuda et al.

    4-Nonylphenols and 4-tert-octylphenol in water and fish from rivers flowing into Lake Biwa

    Chemosphere

    (2000)
  • C. Wahlberg et al.

    Determination of nonylphenol and nonylphenol ethoxylates as their pentafluorobenzoates in water, sewage sludge and biota

    Chemosphere

    (1990)
  • M. Ahel et al.

    Determination of alkylphenols and alkylphenol mono- and diethoxylates in environmental samples by high-performance liquid chromatography

    Anal Chem

    (1985)
  • M. Ahel et al.

    Estrogenic metabolites of alkylphenol olyethoxylates in secondary sewage effluents and rivers

    Water Sci Technol

    (2000)
  • E.R. Bennett et al.

    Distribution of degradation products of alkylphenol ethoxylates near sewage treatment plants in the Lower Great Lakes, North America

    Environ Toxicol Chem

    (2000)
  • C. Crescenzi et al.

    Determination of non-ionic polyethoxylate surfactants in environmental waters by liquid chromatography/electrospray mass spectrometry

    Anal Chem

    (1995)
  • J. Dachs et al.

    Occurrence of estrogenic nonylphenols in the urban and coastal atmosphere of the lower Hudson River estuary

    Environ Sci Technol

    (1999)
  • A. Di Corcia et al.

    Monitoring aromatic surfactants and their biodegradation intermediates in raw and treated sewages by solid-phase extraction and liquid chromatography

    Environ Sci Technol

    (1994)
  • A. Di Corcia et al.

    Characterization of recalcitrant intermediates from biotransformation of the branched alkyl side chain of nonylphenol ethoxylate surfactants

    Environ Sci Technol

    (1998)
  • J. Ejlertsson et al.

    Anaerobic degradation of nonylphenol mono- and diethoxylates in digestor sludge, landfill municipal solid waste and landfill sludge

    Environ Sci Technol

    (1999)
  • P.L. Ferguson et al.

    Distribution and fate of neutral alkylphenol ethoxylate metabolites in a sewage-impacted urban estuary

    Environ Sci Technol

    (2001)
  • J.A. Field et al.

    Nonylphenol polyethoxy carboxylate metabolites of non-ionic surfactants in US paper mill effluents, municipal sewage treatment plant effluents, and river waters

    Environ Sci Technol

    (1996)
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